Sunday/Monday Ocean-Effect Snow Event Underway on Cape Cod

What is Ocean-Effect Snow? Ocean-effect snow occurs when cold air flows over relatively warmer ocean waters. The temperature contrast between the cold air and warm water causes moisture to rise and condense, forming snow bands. This phenomenon is similar to lake-effect snow but is caused by the ocean instead of a lake.

Why is Cape Cod Susceptible? Cape Cod is particularly vulnerable due to its geographic position. As cold northwest to northerly winds blow over the warmer waters of Cape Cod Bay and the Atlantic, the moisture picked up from the ocean creates snow that can spray over a broad area, but the heaviest of which usually falls in narrow, localized bands within a broader area of light snow and flurries. The unique curvature of the Cape can also amplify snow production.

Fluffy Snow and Fast Accumulations The snow from ocean-effect events tends to be very fluffy. This is because the air is often very cold, which leads to lower water content in the snowflakes. These “light and airy” snowflakes accumulate quickly, even when precipitation rates are moderate.

Specifics for This Event

• Current Observations: As of Sunday, 10 AM, Chatham, MA, has already received 1.5 inches of snow.
• Forecast Totals: Expect a coating to 2 inches of accumulation across the South Shore (eastern Plymouth County) and Cape Cod, with 1–2 inches likely for most of the Cape. Falmouth to Woods Hole will see less snow due to the current northwest wind, which will shift northerly later today and tonight.
• Localized Impact: This event will produce variable, localized effects, typical of ocean-effect snow. Some areas could see variations in totals over just a few miles.
• End Time: Most of the snow is expected to taper off by noon Monday.
• Travel and Safety: Snow-covered roads may require plowing and treatment in affected areas.

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